Allegra and James are at ORNL today starting the first test print of the DDM Car’s chassis/tub. While the final car will be printed as a monocoque (body, chassis, et all as a single piece) we are starting with a carbon fiber infused ABS print of just a tub structure in order to build a test mule, which will rather simply be a chassis + powertrain capable of driving around and used to test the integrity of part, prove out the fastening and attachment techniques, and generally answer any other questions we have!
Now that we have enough material in house, we are ready to start the print!
But first, we made sure to set up the GoPro to take time lapsed footage of the near 48hour process.
Also, when you first turn on the extruder and get the material heated up, there is a slight purging process to make sure the bead is at optimal conditions when you start the print. Here is a picture of what comes out. This is a great demonstration of how thick the bead of material is at the moment. The ORNL team is currently coming out with some different nozzles to vary the bead size, so stay tuned for that in the next couple months! It may allow us more flexibility in the structures that are possible with this printing method.
With that complete, it’s time to get started. The printer laid down a bead of the outer perimeter first, and will work in layers of the entire part from bottom to top.
After an hour, it has laid down the entire first layer of the print! (One example of how much work there is still to go to get this process working speedily enough to be a major competitor in manufacturing! –but still way better than the 2500hours it took for just the body of the Urbee car:
It will do two solid layers, then 2 layers at “25% infill” and then two more to create the solid base of the part, from there it will begin to move up into the features. Here is a picture of the rendering of the part as it should look when completed:
For those of you who are interested in bead size and structure, here is a close up of the front end after completing just the first layer:
Another exciting bonus is that today, as it prints, ORNL has 2 thermal cameras hooked up to study the temperature gradients of the part, which will later allow the team to analyze Z-strength and bonding of the layers.
An update to this post:
Unfortunately we were unable to complete the first test piece as intended above at this time due to a couple of issues in the printing process. (Mainly from the contraction of the part as it cooled due to the large nature of the piece, and also the software used to generate the g-code was struggling with the translation.. please see discussions on the materials topic in the upcoming days for more details)
This is a great learning experience on a very, very new technology and process that has not been done before -- so while it did not come out perfectly on our first attempt, we are very excited about the things we are learning and will be at it again shortly! Here is a quick picture of the printing progress a little bit before it went wonky and we made the call to try again at a later date (at about 9 full layers--looking cool!)